Effects of spinosad and Bacillus thuringiensis israelensis on a natural population of Daphnia pulex in field microcosms

摘要: Spinosad, a candidate biological larvicide for mosquito control, was evaluated its effects on field population of Daphnia pulex, using Bacillus thuringiensis serovar israelensis (Bti) as reference larvicide. Microcosms (125 L enclosures) were placed in shallow temporary oligohaline marsh where D. pulex present. Three concentrations spinosad (8, 17 and 33 μg L−1) two Bti (0.16 0.50 μL applied (5 replicates per concentration, including the controls). Effects larvicides after 2, 4, 7, 14 21 d exposure, through measurements abundance individual size. Dissipation from water phase rapid. Four days treatment, residue concentration represented 11.8%, 3.9% 12.7% initial exposure level nominal 8, L−1, respectively. Spinosyns A D dissipated at similar rates. Analysis size structure showed an impact spinosad. Both survival affected. However, lowest (8 L−1), recovered first week. In microcosms treated with Bti, not affected but changed d. As compared to laboratory tests, use situ improved environmental risk assessment larvicides, taking into account influence factors (e.g., temperature, light, salinity) intrinsic capacity recovery under conditions.